American passport. ED visa extension ends December 24th. My flight home is december 26th.

The person who handles the paperwork for my school is out of the country, and won't return until the 23rd. I was planning on going to immigration on the 22nd. My new plan is to get the paperwork on the 23rd and go to immigration on Monday the 25th, Christmas. I read going in on the first business day after a stamp expires is ok, no fine imposed.

I see conflicting information about getting a 7 day 'get out of thailand' stamp. Do I need to file for and get denied an extention to get the stamp or will immigration just give me one on the 25th?

Also, if i just overstay 2 days after canceling my visa, and pay fine at the airport, will a 2 day overstay affect any future ED visa applications? I am planning on returning next year and attending university.